HarmonyOS学习路之方舟开发框架—学习ArkTS语言（状态管理 四）

// 允许@ObjectLink装饰的数据属性赋值
this.objLink.a= ...
// 不允许@ObjectLink装饰的数据自身赋值
this.objLink= ...

class ClassA {
  public c: number;

  constructor(c: number) {
    this.c = c;
  }
}

@Observed
class ClassB {
  public a: ClassA;
  public b: number;

  constructor(a: ClassA, b: number) {
    this.a = a;
    this.b = b;
  }
}

@ObjectLink b: ClassB

// 赋值变化可以被观察到
this.b.a = new ClassA(5)
this.b.b = 5

// ClassA没有被@Observed装饰，其属性的变化观察不到
this.b.a.c = 5

// objectLinkNestedObjects.ets
let NextID: number = 1;

@Observed
class ClassA {
  public id: number;
  public c: number;

  constructor(c: number) {
    this.id = NextID++;
    this.c = c;
  }
}

@Observed
class ClassB {
  public a: ClassA;

  constructor(a: ClassA) {
    this.a = a;
  }
}

@Component
struct ViewA {
  label: string = 'ViewA1';
  @ObjectLink a: ClassA;

  build() {
    Row() {
      Button(`ViewA [${this.label}] this.a.c=${this.a.c} +1`)
        .onClick(() => {
          this.a.c += 1;
        })
    }
  }
}

@Entry
@Component
struct ViewB {
  @State b: ClassB = new ClassB(new ClassA(0));

  build() {
    Column() {
      ViewA({ label: 'ViewA #1', a: this.b.a })
      ViewA({ label: 'ViewA #2', a: this.b.a })

      Button(`ViewB: this.b.a.c+= 1`)
        .onClick(() => {
          this.b.a.c += 1;
        })
      Button(`ViewB: this.b.a = new ClassA(0)`)
        .onClick(() => {
          this.b.a = new ClassA(0);
        })
      Button(`ViewB: this.b = new ClassB(ClassA(0))`)
        .onClick(() => {
          this.b = new ClassB(new ClassA(0));
        })
    }
  }
}

@Component
struct ViewA {
  // 子组件ViewA的@ObjectLink的类型是ClassA
  @ObjectLink a: ClassA;
  label: string = 'ViewA1';

  build() {
    Row() {
      Button(`ViewA [${this.label}] this.a.c = ${this.a.c} +1`)
        .onClick(() => {
          this.a.c += 1;
        })
    }
  }
}

@Entry
@Component
struct ViewB {
  // ViewB中有@State装饰的ClassA[]
  @State arrA: ClassA[] = [new ClassA(0), new ClassA(0)];

  build() {
    Column() {
      ForEach(this.arrA,
        (item) => {
          ViewA({ label: `#${item.id}`, a: item })
        },
        (item) => item.id.toString()
      )
      // 使用@State装饰的数组的数组项初始化@ObjectLink，其中数组项是被@Observed装饰的ClassA的实例
      ViewA({ label: `ViewA this.arrA[first]`, a: this.arrA[0] })
      ViewA({ label: `ViewA this.arrA[last]`, a: this.arrA[this.arrA.length-1] })

      Button(`ViewB: reset array`)
        .onClick(() => {
          this.arrA = [new ClassA(0), new ClassA(0)];
        })
      Button(`ViewB: push`)
        .onClick(() => {
          this.arrA.push(new ClassA(0))
        })
      Button(`ViewB: shift`)
        .onClick(() => {
          this.arrA.shift()
        })
      Button(`ViewB: chg item property in middle`)
        .onClick(() => {
          this.arrA[Math.floor(this.arrA.length / 2)].c = 10;
        })
      Button(`ViewB: chg item property in middle`)
        .onClick(() => {
          this.arrA[Math.floor(this.arrA.length / 2)] = new ClassA(11);
        })
    }
  }
}

@Observed
class StringArray extends Array<String> {
}

@Observed
class StringArray extends Array<String> {
}

@Component
struct ItemPage {
  @ObjectLink itemArr: StringArray;

  build() {
    Row() {
      Text('ItemPage')
        .width(100).height(100)

      ForEach(this.itemArr,
        item => {
          Text(item)
            .width(100).height(100)
        },
        item => item
      )
    }
  }
}

@Entry
@Component
struct IndexPage {
  @State arr: Array<StringArray> = [new StringArray(), new StringArray(), new StringArray()];

  build() {
    Column() {
      ItemPage({ itemArr: this.arr[0] })
      ItemPage({ itemArr: this.arr[1] })
      ItemPage({ itemArr: this.arr[2] })

      Divider()

      ForEach(this.arr,
        itemArr => {
          ItemPage({ itemArr: itemArr })
        },
        itemArr => itemArr[0]
      )

      Divider()

      Button('update')
        .onClick(() => {
          console.error('Update all items in arr');
          if (this.arr[0][0] !== undefined) {
            // 正常情况下需要有一个真实的ID来与ForEach一起使用，但此处没有
            // 因此需要确保推送的字符串是唯一的。
            this.arr[0].push(`${this.arr[0].slice(-1).pop()}${this.arr[0].slice(-1).pop()}`);
            this.arr[1].push(`${this.arr[1].slice(-1).pop()}${this.arr[1].slice(-1).pop()}`);
            this.arr[2].push(`${this.arr[2].slice(-1).pop()}${this.arr[2].slice(-1).pop()}`);
          } else {
            this.arr[0].push('Hello');
            this.arr[1].push('World');
            this.arr[2].push('!');
          }
        })
    }
  }
}